The present invention is directed to the generation of static pressure by squeezing samples between a pair of anvils and more particularly to achieving higher static pressure utilizing isotopically-pure diamond anvils.
The generation of high pressure for research and development exploratory work has been influenced heavily by apparatus design and strength of materials. Professor Bridgman of Harvard found that he could reach pressures of about 100 Kbar by squeezing thinned samples between flat blocks. This work, starting about 50 years ago, led to the development of the famous Bridgman anvil. Bridgman recognized that if harder materials, such as sintered diamonds, were used for anvils, even higher pressures could be reached. Von Valkenburg and Weir at the National Bureau of Standards (NBS), Washington, D.C., unaware of Bridgman's recommendation, made Bridgman anvils out of single crystal diamond in 1959. This started a revolution in high pressure work. Diamond anvil cells now are ubiquitous devices used throughout the world in high pressure research.
Twenty years later, NBS high pressure cells achieved pressures up to 500 Kbar utilizing anvils, each of which was a brilliant cut diamond of about one-third carat, the culet being polished to produce a flat of about 0.002 mm.sup.2 in area. This flat generally is the (100) plane, since the normal plane of a brilliant cut is (100).
Pressures approaching 5,000 Kbar, equal to the pressure at the center of the earth, have been reported by Ruoff et al, "Optical Properties of Diamond at Pressures Comparable to the Earth's Center", Proceedings of the Second International Conference, New Diamond Science and Technology, Edited by Messier et al, Sep. 23-27, Washington, D.C. Materials Research Society, Pittsburgh, Pa., the disclosure of which is expressly incorporated herein by reference. Still higher pressures are desired. Experiments performed at 4,000 Kbar and higher results in the expensive anvils being broken in virtually every run. Thus, the need in the art for apparatus that is capable of producing these or even higher pressures without loss or breakage of the diamond anvils.